1 TURBO MACHINES (Unit 1 & Unit 2) DR. G.R. SRINIVASA
2 TURBO MACHINES VTU Syllabus Subject Code : 06ME55 IA Marks No. of Lecture Hrs./Week : 04 Total No.of Lecture Hrs. : 52 : 25 Exam Hours : 03 Exam Marks : 100 PART – A UNIT – 1 INTRODUCTION: Definition of a Turbomachine; parts of a Turbomachine; Comparison with positive displacement machine; Classification: Application of First and Second Laws to Turbomachines, Efficiencies. Dimensionless parameters and their physical significance; Effect of Reynolds number; Specific speed; Illustrative examples on dimensional analysis and model studies. 6 Hours UNIT – 2 ENERGY TRANSFER IN TURBO MACHINE: Euler Turbine equation; Alternate form of Euler turbine equation – components of energy transfer; Degree of reaction; General analysis of a Turbo machine – effect of blade discharge angle on energy transfer and degree of reaction; General analysis of centrifugal pumps and compressors – Effect of blade discharge angle on performance; Theoretical head – capacity relationship 6 Hours UNIT – 3 GENERAL ANALYSIS OF TURBO MACHINES: Axial flow compressors and pumps – general expression for degree of reaction; velocity triangles for different values of degree of reaction; General analysis of axial and radial flow turbines – Utilization factor; Vane efficiency; Relation between utilization factor and degree of reaction; condition for maximum utilization factor – optimum blade speed ratio for different types of turbines 7 Hours UNIT – 4 THERMODYNAMICS OF FLUID FLOW AND THERMODYNAMIC ANALYSIS OF COMPRESSION AND EXPANSION PROCESSES: Sonic velocity and Mach number; Classification of fluid flow based on Mach number; Stagnation and static properties and their relations; Compression process – Overall isentropic efficiency of compression; Stage efficiency; Comparison and relation between overall efficiency and stage efficiency; Polytrophic efficiency; Preheat factor, Expansion Process – Overall isentropic efficiency for a turbine; Stage efficiency for a turbine; Comparison and relation between stage efficiency and overall efficiency for expansion process, polytrophic efficiency of expansion; Reheat factor for expansion process. 7 Hours
3 PART – B UNIT – 5 CENTRIFUGAL COMPRESSORS: Classification; Expression for overall pressure ratio developed; Blade angles at impeller eye root and eye tip; Slip factor and power input factor; width of the impeller channel; Compressibility effect – need for pre-whirl vanes; Diffuser design: Flow in the vaneless space, determination of diffuser inlet vane angle, width and length of the diffuser passages; Surging of centrifugal compressors; AXIAL FLOW COMPRESSORS: Classification; Expression for Pressure ratio developed per stage – work done factor, radial equilibrium conditions. UNIT – 6 CENTRIFUGAL PUMPS: 6 Hours Definition of terms used in the design of centrifugal pumps like manometric head, suction head, delivery head, pressure rise, manometric efficiency, hydraulic efficiency, volumetric efficiency, overall efficiency, multistage centrifugal pumps, minimum starting speed, slip, priming, cavitation, NPSH. 6 Hours UNIT – 7 STEAM TURBINES: Classification, Single stage impulse turbine; Condition for maximum blade efficiency, stage efficiency, Compounding – Need for compounding, method of compounding. Impulse Staging – Condition of maximum utilization factor for multi stage turbine with equiangular blades; effect of blades and nozzle losses. Reaction turbine; Parson’s reaction turbine, condition for maximum blade efficiency, reaction staging. 7 Hours UNIT – 8 HYDRAULIC TURBINES: Classification; Pelton Turbine-velocity triangles, Design parameters, turbine efficiency, volumetric efficiency; Francis turbine – velocity triangles, runner shapes for different blade speeds, Design of Francis turbine; Function of a Draft tube, types of draft tubes; Kaplan and Propeller turbines – Velocity triangles and design parameters. 7 Hours TEXT BOOKS: 1. 2. An Introduction to energy conversion, Volume III – Turbo machinery, V. Kadambi and Manohar Prasad, New Age International Publishers (P) Ltd. nd “Turbines, Compressors & Fans”, S.M. Yahya, Tata-McGraw Hill Co., 2 Edition (2002). REFERENCE BOOKS: 1. 2. 3. 4. “Principles of Turbo Machinery”, D.G. Shepherd, The Macmillan Company (1964). Fundamentals of Turbomachinery: William W. Perg, John Wiley & Sons, Inc. 2008. A Text book of Turbo Machines - M.S.Govindgouda & A.M. Nagaraj-M.M.Publications-IV Edition-2008 “Fluid Machinery” B.K. Venkanna, PHI.
4 In these lectures, we will learn different type of turbo machines, their action, as power generating turbo machines or power absorbing turbo machines. You will be shown schematic diagrams of various turbo machines with flow directions. DEFINITION: A turbo machine is a device in which energy transfer occurs between a flowing fluid and rotating element due to dynamic action. This results in change of pressure and momentum of the fluid. TYPE: If the fluid transfers energy for the rotation of the impeller, fixed on the shaft, it is known as power generating turbo machine. If the machine transfers energy in the form of angular momentum fed to the fluid from the rotating impeller, fixed on the shaft, it is known as power absorbing turbo machine. Examples of a turbo machine: The figures 1 & 2 show a typical turbo charger used in diesel engines to improve its thermal efficiency by increasing the pressure of air pumped into engine combustion chamber. Fig. 1